Rates of severe childhood hand, foot and mouth disease, or HFMD, have declined significantly in Chengdu, China, since the introduction of a localized pediatric enterovirus 71 immunization program in 2016, according to results from a longitudinal surveillance study published in Clinical Infectious Diseases.
“Enterovirus 71 (EV71) is a major causative agent of HFMD, associated with severe manifestations of the illness,” researchers wrote. “The most prevalent enterovirus serotypes causing HFMD in China are EV71 and coxsackievirus A16 (CA16), with EV71 implicated in 70% of severe cases and 92% of deaths.”
In December 2015, a monovalent, inactivated, whole-virus vaccine against EV71 was licensed in China. Researchers analyzed the number of cases of severe HFMD attributable to EV71, CA16 and other enteroviruses in Chengdu — a “major transmission center in China,” they said — following the vaccine’s introduction in 2016.
From 2017 to 2018, the average HFMD incident rate was 60% (95% prediction interval [PI], 41%-72%) lower than predicted in the absence of immunization — equivalent to 6,911 (95% PI, 3,246-11,542) cases averted over the 2-year period. Overall, 52% (95% PI, 0.42-0.6) fewer severe HFMD cases were observed than predicted, but the incidence rate of non-EV71 and CA16-induced HFMD was elevated in 2018.
Kevin Messacar, MD, a pediatric infectious disease physician and researcher at Children’s Hospital Colorado and the University of Colorado, told Healio that it is unclear whether a recent 2018 outbreak of EV71 in Colorado was a sporadic incident or “foreboding of future circulation in the United States.”
“It is useful to know that a vaccine approach could be effective at preventing disease if EV71 were to increase in prevalence” in the United States, said Messacar, who was uninvolved in the study.
Two of the study’s major limitations were that only a small portion of cases underwent serotype determination, and that the post-vaccine period lasted only for a short duration, the authors noted.
EV71 can cause a number of severe diseases, including acute flaccid myelitis, brainstem encephalitis and even death, according to Messacar, who believes the vaccine may have the potential to “prevent serious morbidity” caused by neurologic presentations of the virus.
“Rates of EV71 infection could be expected to continue to decline if the vaccine program is successful.” Messacar said. “However, as HFMD can be caused by various other nonpolio enteroviruses, it is less certain what will happen with the overall rate of HFMD.” – by Eamon Dreisbach
For more information:
Messacar K, et al. Lancet Infect Dis. 2019;doi:10.1016/S1473-3099(19)30632-2.
Disclosures: Messacar reports no relevant financial disclosures. Please see the study for all authors’ relevant financial disclosures.